J. Nig. Soc. Phys. Sci. 3 (2021) 256–261

Journal of the
Nigerian Society

of Physical
Sciences

Influence of Silicon Nanoparticle on the Electrical Properties of
Heterostructured CdTe/CdS thin films based Photovoltaic Device

A. A. Faremia,∗, S. S. Oluyamob, K. D. Adedayob, Y. A. Odusoteb, O. I. Olusolab

aDepartment of Physics, Federal University, Oye-Ekiti, Nigeria
bFederal University of Technology, Akure, Nigeria

Abstract

This paper presents the influence of silicon nanoparticles at the interface of heterostructured Cadmium telluride and cadmium sulfide thin films
based photovoltaic device with improved electrical parameters leading to tremendous improvement in CdS/CdTe thin film based solar cells per-
formance. The films of CdTe, CdS and Si were electrodeposited using electrodeposition technique to form a heterostructured CdTe/Si/CdS/FTO.
The films respective structural properties were also examined using X-ray Diffractometer (XRD) before forming a heterostructured material. The
heterostructured CdTe/Si/CdS/FTO and the structure without the inclusion of silicon nanoparticle were examined using electrometer for the ex-
traction of electrical parameters such open circuit voltage (VOC ), short circuit current density (JS C ), and fill factor (FF). Although a large body
of experimental results are available to date on the optoelectronics properties of the materials. However, there is relatively low research studies
or works on the electrical properties of the materials. Therefore, we formed heterostructured based photovoltaic device and characterized the
structure to determine useful electrical properties. The value obtained for VOC , JS C and FF are 418 mV, 25 mA/cm2 and 0.72 which are indicative
of pin holes free semiconductor materials and no leakage path emerging from high-grade materials used in the deposition of heterostructured
CdTe/Si/CdS.

DOI:10.46481/jnsps.2021.267

Keywords: Silicon nanoparticles, Electrodeposition technique, Heterostructured based photovoltaic, Electrical properties

Article History :
Received: 23 June 2021
Received in revised form: 23 July 2021
Accepted for publication: 01 August 2021
Published: 29 August 2021

c©2021 Journal of the Nigerian Society of Physical Sciences. All rights reserved.
Communicated by: E. Edward Anand

1. Introduction

The use of p-type CdTe, n-type CdS and transparent con-
ducting substrates such as fluorine doped tin oxide and indium
doped tin oxide for the formation of heterostructured CdTe/CdS
based solar cells have received considerable attention because
of their notable performance in energy conversion devices [1-
3]. The suitability of CdS thin film as a good window layer

∗Corresponding author tel. no: +2347033712587
Email address: abass.faremi@fuoye.edu.ng (A. A. Faremi )

material capable of providing excellent receptive surface to ab-
sorber layer materials such as p-type cadmium telluride (CdTe),
p-type copper indium selenide (CuInSe2), etc is owned to its
high electron affinity [3]. Despite the potential of CdS in the
formation of heterojunction based solar cells, there is need to
treat its surface for better receptive surface which offer better
improvement on the electrical parameters of the photovoltaic
solar cells [4-6]. CdTe thin film as one of the primary candi-
dates in the field of photovoltaic technology has gained world-
wide prominence owning to its near ideal bandgap energy of
1.45 eV for the absorption of photons [6]. Interdiffusion of tel-

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Faremi et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 256–261 257

lurium as a dopant in CdTe has been reported as a hindrance
to the performance of CdTe based devices [7]. However, a lot
of improvement have been made to prevent such as an inter-
diffusion such as post-heat treatment of the films surface in the
presence of cadmium chloride or oxygen [6], [8], [9]. Silicon
thin film as a leading and the most building block for electron-
ics has been report being a useful material to set an enabling
environment for CdTe/CdS based solar cells [7]. We there-
fore use silicon nanoparticles as a preventive measure to inter-
diffusion of tellurium since we aimed at forming heterojunc-
tion of CdTe/CdS. The films of CdTe, CdS and Si have been
prepared by various techniques, including sputtering, spray-
pyrolysis, chemical bath deposition, Sol-gel, close space subli-
mation, ion implantation and electrodeposition [1], [2], [10-12].
Among the various techniques available for the synthesis of
these materials, electrodeposition and sol-gel techniques have
been reported as viable techniques over other processes because
of their simplicity in term of material growth [13-15]. However,
in a typical sol-gel technique, the chosen reagents for a thin film
need to undergo series of hydrolysis and polymerization reac-
tions to form a solution bath [16]. The series of process require
in the formation of solution bath make the technique to be more
less cost-effective than electrodeposition technique. The tech-
nique has also gained research attention due to its possibility
of scaling down bulk Silicon to either thin film or nanoparti-
cles [17], [18]. In our study, we employed electrodeposition
in the synthesis of the heterostructured CdTe/Si/CdS because
of its relatively simple, easy, robust, easily scalable, bath self-
purification and economically viable for large area production
of photovoltaic devices [4], [19], [20].

2. Materials and Method

The film of CdS sourced from the solution of high-grade
Cadmium Sulphate (3CdSO4.8H2O, 99%) and thiourea (CS(NH3)2, 99%)
without further purification was electrodeposited at a cathodic
potential of 1400 mV on a thoroughly degreased conducting
FTO/substrate of 3.2 by 3 cm2 in dimension. After deposition,
the material was subjected to curing at substrate temperature of
400o C in 20 minutes and further purified in deionized water so
that the surface could provide a perfect receptive surface for the
other materials since we aimed at forming a heterostructured
device. Silicon powder of 2 grams by weight was dispensed in
500 ml beaker containing 400 ml of deionized water and mag-
netically stirred for 2hrs. The electrolytic bath of silicon powder
was electrodeposited potentiostatically at cathodic potential of
1000 mV on the deposited CdS. The structure of Si/CdS/FTO
was also further cured at the same substrate temperature and
washed thoroughly to remove possible undissolved particles on
the surface to enable proper adherent of CdTe film sourced from
the solution of high-grade Cadmium Sulphate (3CdSO4.8H2O,
99%) and tellurium dioxide (TeO2, 99%). The electrolytic bath
of CdTe, CdS and Si was adjusted and controlled using am-
monium solution and pH probe. The pH value of the bath
was 2.0 since the employed technique is favourable in acidic
medium. Deposition took place at bath temperature of 80 oC
in 60 minutes using working electrode with carbon as counter

electrode. The films of CdTe, CdS, Si, the heterostructure of
CdTe/Si/CdS/FTO and structure without the inclusion of sili-
con was also fabricated. The structure was examining for their
structural and electrical properties using XRD and Electrometer
probe. The particle crystallite size and the electrical parameters
of the electrodeposited structure were extracted using equation
1-5

D =
Kλ
βcosθ

(1)

where λ is x-ray wavelength in A
◦

, K is a Scherrer constant
(K=0.9), β is measured at half-maximum of the diffraction peak
and θ is the Bragg’s angle and D is the particle size or crys-
talline size.

η=
Pmax
Pin

=
Vm Im
Pin

(2)

Where Pmax is the maximum power out, Pin is the maximum
power input (A solar simulator made from a 25 W incandes-
cent light bulb was employed for this. The distance between
the bulb and the surface of the cells was approximately 9.2 cm,
which good enough for maximum radiance without significant
heat transfer. The radiance intensity of the simulator used, con-
sidering sample distance from source as 9.2 cm was estimated
at 220 W/m2.), Vm is the maximum voltage power and Im is the
maximum current power

F F=
Pmax

Voc Isc
=

Vm Im
Voc Isc

(3)

Where FF is the fill factor, VOC is the open circuit voltage and
IS C is the short circuit current
The conversion efficiency can also be estimated by combining
equation 1 and 2 to form equation 3

η=
F F×Voc×Isc

Pin
(4)

It is important to note the relationship between Jsc and Isc as the
two parameters are often used.

Jsc=
Isc
A

(5)

Where A is the surface area of the heterostructured CdTe/Si/CdS
which is estimated as 0.000096 m2.

3. Result and Discussion

3.1. Structural characterization of CdTe, CdS thin films and Si
nanoparticle

Figure 1 reveals eight basic peaks (111), (210), (211), (220),
(222), (321), (411) and (420) with their corresponding diffrac-
tion angles 22.71o, 28.01o, 30.00o, 37.00o, 48.80o, 50.00o, 57.88o

and 60.24o. The different peaks as observed in the XRD pattern
of CdTe, CdS and Si indicated structural transformation from
single phase to polycrystalline. There is no noticeable broad
hump in the structures of polycrystalline CdTe, CdS and Si.
Figure 2 reveals similar structural transformation with six basic

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Faremi et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 256–261 258

Figure 1. XRD plot for cadmium telluride thin film prepared using 1400
mV cathodic deposition technique, with peaks characteristics of poly-
crystalline cadmium telluride

Figure 2. XRD plot for cadmium sulfide thin film prepared using 1400
mV cathodic deposition technique, with peaks characteristics of poly-
crystalline cadmium telluride

peaks (111), (220), (311), (400), (420) and (422), as a func-
tion of diffraction angles 20.97o, 34.01o, 41.08o, 50.00o, 54.68o

and 58.72o. In Figure 2 and 3, three prominent peaks that’s
(111), (220) and (311) are observed which holds potentiality
to polycrystalline cadmium sulfide (CdS) thin films and Silicon
(Si) nanoparticles [21], [22]. Peak 111 as a dominant peak in
both Figures 1, 2 and 3, revealed the preferred orientation of the
structures being the most intense peak which is also an indica-
tion of particles crystallization (highly and randomly oriented)
and zinc blende structure. The full width at half maximum of
CdTe CdS and Si were obtained by broadening most intense
peak through a gaussian fitting which was used to determine
the particle crystallite size using Sherer’s equation. The esti-
mated particle crystallite size of CdTe, CdS and Si are 11.98,
14.08 and 89 nm respectively. The estimated particle crystallite
sizes of both CdTe, CdS and Si agreed with the previous work
[21], [22], [24], [25].

Figure 3. XRD plot for electrodeposited silicon nanoparticles prepared
using 1000 mV cathodic potential, with peaks characteristics of poly-
crystalline silicon

Figure 4. SEM micrograph of electrodeposited CdTe thin film

3.2. Morphological characterization of CdTe, CdS thin films
and Si nanoparticle

The electrodeposited materials are uniformly distributed on
the substrate and the grains as depicted in figure 4-6 have spher-
ical shape with faceted edges. The uniformity of materials re-
veals the significance of cathodic deposition technique over an-
odic technique [26]. However, the nucleation CdTe, CdS and Si
on the well degreased FTO/substrate show uniform distribution
of grains and relatively little agglomeration. Such a uniformity
in the grains distribution could reducing electron trapping in
the lattice site resulting to improved electrical parameters [22],
[23]. The little agglomeration in the SEM micrographs of the
materials agrees with previous works [3], [4], [26], [27].

3.3. Electrical characterization of heterostructured CdTe/Si/CdS
and CdTe/CdS

In order to characterize the electrical behaviour at the interface
of the heterostructured devices, it is necessary to carry out I-V
characterization under illumination and dark conditions which
helps to harness the potentials of heterostructured photovoltaic
devices [28], [29]. Figure 7 revealed the electrical parameters

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Faremi et al. / J. Nig. Soc. Phys. Sci. 3 (2021) 256–261 259

Figure 5. SEM micrograph of electrodeposited CdS thin film

Figure 6. SEM micrograph of electrodeposited Si thin film

of CdTe/Si/CdS/FTO based photovoltaic measured under illu-
mination condition using electrometer. The fill factor as an im-
portant photovoltaic parameter which characterized the grade
and the curve fitness of the device revealed the potential of the
structures. The slight change in the electrical parameters as de-
picted in figure 8 was as result of measurement condition, dark.
Despite the variation in the parameters, there is tremendous im-
provement in the electrical conductivity of the device. Such
improvement could be attributed to overcoming the barrier po-
tential or potential hill using forward bias voltage. Figure 9 and
10 revealed the electrical parameters of the device without the
inclusion of the silicon nanoparticle. The injection of silicon
nanoparticles in the structure also aided the device electrical
parameters such as open circuit voltage (Voc), short circuit cur-
rent density (Jsc), and ll factor (FF) of the heterostructure de-
vices as shown in Table 1. The structure exhibits PIN-diode like
characteristic due to the injection of silicon nanoparticles which
serve as an intrinsic material between the p-type CdTe and n-
type CdS. Such a structure could act as a good photodetector,
high voltage rectifier and radio frequency switches. The high
values of the extracted open circuit voltage (Voc), short circuit
current density (Jsc) and ll factor (FF) showed that pinhole free
semiconductor materials have been successfully fabricated and
their suitability have been confirmed in the electrical properties

Figure 7. Electrical properties of CdTe/Si/CdS/FTO based photovoltaic
structure measured under illumination condition using electrometer

Figure 8. Electrical properties of CdTe/Si/CdS/FTO based photovoltaic
structure measured under dark condition using electrometer

Figure 9. Electrical properties of CdTe/CdS/FTO based photovoltaic
structure measured under illumination condition using electrometer

of the heterostructured CdTe/CdS based photovoltaic.

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Table 1. Quantitative electrical parameters of heterostructured based Photovoltaic device
Heterostructured
CdTe/Si/CdS
Light Dark
VOC
(mV)

JS C
(mA/cm2)

VMax
(mV)

IMax (mA) FF VOC
(mV)

J S C
(mA/cm2)

VMax
(mV)

IMax (mA) FF

418 25.02 395 17.17 0.72 367 12.85 0.339 9.25 0.69
Heterostructured
CdTe/CdS
Light Dark
VOC
(mV)

JS C
(mA/cm2)

VMax
(mV)

IMax (mA) FF VOC
(mV)

JS C
(mA/cm2)

VMax
(V)

IMax (mA) FF

398 18.58 362 13.10 0.66 338 9.55 0.297 6.33 0.61

Figure 10. Electrical parameters of the fabricated CdTe/Si/CdS and
CdTe/CdS under illumination and dark conditions

4. Conclusion

The potential of electrodeposition technique in the fabrica-
tion of heterostructure based photovoltaic has made a signifi-
cant improvement in the electrical properties of the CdTe/Si/CdS
and CdTe/CdS configurations. The probe into electrical be-
haviour at the interface of the heterostructured based device
has revealed the successive development of photovoltaic de-
vices. The injection of silicon into the structure also offer bet-
ter and improved photovoltaic parameters leading to high value
in both open circuit voltage and short circuit current density.
Such increase in the photovoltaic parameters are indicative of
high-grade reagents used which have also resulted to no leakage
path and pinhole free compound semiconducting materials. The
structural analysis of the films revealed structural transforma-
tion from single phase to polycrystalline which is an evidence
that we have successfully fabricated polycrystalline CdTe, CdS
and Si

Acknowledgments

The authors wish to acknowledge the financial support of
Tertiary Education Trust Fund (TETFund) of Nigeria through
Federal University Oye-Ekiti and the efforts of The Federal

University of Technology, Akure, Nigeria for providing the re-
search laboratories for performing the experiments and research
facilities used for data acquisition.

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